PROJECT SUMMARY PCB analysis for research purposes is labor-intensive, requires specialized instrumentation, and depends on excellent quality control procedures. Because the Analytical Core provides the trained staff, maintains the instruments and facilities, and provides methods to assure accuracy, precision, representativeness, comparability, and reproducibility, the isrp research projects are able to make high impact discoveries, publish their results in peer-review journals, and more quickly provide scientific guidance regarding PCBs in the environment and their effect on human health. The Analytical Core supports the research of the isrp by extracting and analyzing samples for all 209 PCBs and for individual compounds in complex matrices including air samples; harbor sediment; human blood serum; urine; laboratory animal tissues; plant tissues; soils; sludge; laboratory solutions, building materials, paint, and furniture. Each year the Analytical Core will complete thousands of such measurements as well as hundreds of quality control measurements and method development measurements. The Analytical Core provides detailed quality control guidance and collaborates closely with isrp researchers to determine appropriate methods for quality assurance control. Analyses for PCB congeners in environmental matrices includes routine use of surrogate standards injected in every sample to assess and correct for analytical efficiency; internal standards for quantification; duplicate injections; laboratory blanks, calibration standards, and frequent analysis of materials with certified concentrations of PCBs. The rigor of the QC/QA protocol is unusual for PCB analysis but provides the critical foundation for discoveries in the research projects. The Analytical Core has a sustained history of innovation, starting with the development of tandem mass spectrometry for congener-specific analysis of PCBs in environmental and laboratory samples. This method enabled many important discoveries and innovative findings in the isrp, including the ability to link specific toxic properties by compound; accurate determination of the lower molecular weight compounds; and precise measurement of all PCBs. The congener-specific method used by the Analytical Core enabled the discovery of non-Aroclors in the environment. The study of these compounds, which are currently produced through some chemical manufacturing processes, has been a major area of focus since that time. Innovations planned include the development of efficient methods for routine analysis of known and as-yet unknown decay products of PCBs. Although PCBs are very persistent and resistant to decay, many PCBs can be broken down by sunlight and by metabolism in plants, animals and humans. The Analytical Core assists the research projects in measuring those decay products. .